Process of preserving resinous lumber and producing by-products therefrom



March 16 1926.

w. H. MASON fROCESS 0F PRESERVING RESINOUS LUMBER AND PRODUCING BYPRODUCTS THEREFROM 'iled Dec. 1'7, 1920 INVENTOR ATTORNEY PATENT o FFEQ- "WI LIAM H. MASON, or A RE mssrssrrrr.

rnocnss or rnnsnnvme Rnsmoos LUMBER Am) rnonuome BY-rnontr'c'rs THERE- mom.

Application filed December 1 7', 1920. Serial No. 481,475.

T 0 all whom it may concern:

Be, it known that 1, WILLIAM H. MASON, a citizen of the United States, and a resident of Laurel, county of Jones, and ,State of Mississippi, have invented certain new and useful Improvements in Processes of Preserving Resinous Lumber and Producing By-Products Therefrom, of which the following is a specification.

My invention relates to a process of preserving resinous lumber and producing by products therefrom. While the invention is applicable to and will be described in connection with the preserving of yellow pine lumber and the production therefrom of turpentine and pine oils, it is applicable generally to soft woods carrying sufiicient resinous materials to warrant the reclamation thereof.

According to my invention, sawn lumber piled on kiln trucks for kiln drying, with abundant openings provided-for the circulation of the drying medium, is first subjected to treatment with steam in the absence of air, whereby in the. case of yellow pine lumber, for example, substantial yields of turpentine and pine oils are extracted by the steam, and are condensed and saved, and this without substantial additional expenditure of steam or heat or time of treatment, as compared with the customary kiln drying process, and in fact along with the saving of these valuable by-p'roducts there may also be an appreciable saving of time and of expenditure of steam or heat in other forms in the production of kiln dried lumber of good quality and improved in condition by the treatment to which it is subjected.

\Vhile the invention may be utilized in connection with a single kiln, which may be used both as a by-product kiln and as a drying kiln, it best applied in saw-mills having a series of drying kilns, one or more of which are arranged for the carrying on of the initial step of reclaiming the by-products and performing the first conditioning step, after which the lumber on the trucks is removed from the by-product kiln and after preferably being permitted to cool in the open air, the drying is completed in the remaining kilns of the series.

The treatment in the by-product kiln in the case of yellow pine lumber usually requires a period of about ten to twelve hours, thus permitting two charges to be treated per day. The kiln or kilns utilized for this purpose are provided, in addition to the steam heating coils of ordinary drying kilns, which are preferably retained, with pipes for the admission of steamdirectly into the interior of the kiln.

Special precautionsare taken to insure that the door or doors of the byroduct kilns are made ti ht to prevent lea age of air into the kiln, and the kiln is provided with a vapor pipe leading to a suitable condenser for condensing the steam issuing from the kiln, together with any condensable ,vapor carried thereby.

At the commencement of the process the piled lumber on its tracks is introduced into the by-product kiln, which is preferably filled to capacity, and steam is turned into the kiln, which may also be heated as by means of steam coils. At this time the steam can be introduced rapidly, since a considerable quantity of steam is required to heat up the walls of the kiln and the lumber. An air vent is preferably provided at the exit end of the condenser. Air laden with visible vapors issues therefrom, the vapors increasing somewhat in quantity as the temperature of the kiln is raised. These vapors containing air in substantial quantities are not condensable by an ordinary condenser using cold water. When the kiln and its contents have been heated up to somewhat under the boiling point of water, dense clouds of vapor are discharged from the condenser vent. In the case of the kiln referred to in the example given below, this period was about two hours and the fumes given off at and just before the end of this time smelled strongly of turpentine. These dense vapors, like the lesser quantities of vapors appearingduring the earlier stages of heating up the kiln, are not condensable with the ordinary form of cold water condenser. This appears to be due to the presence of some air, since turpentine, which boils over at about 95 C. with steam, does not boil in air until it reaches a temperature of about 153170 C.

If the kiln is kept air tight these fumes quickly subside with the loss of no very great amount of turpentine and the vapor coming over is completely condensed, yielding in the case of yellow pine lumber a mixture of turpentine and pine oils which rises to the surface of the condensed water and is readily lit hit

separated therefrom The condensed water includes moisture from the lumber being' treated as well as steamsupplied to the kiln. When the vapors become condensable it is Possible and desirable to reduce the sup-- ply of steamto the kiln very materially, say to the extent. of retaining only about one-third to one-fifth of the steam supply maintained during the heating 'up period. Care must'be taken to see that the steam is not shut down to such an extent as to, permitentry of air into the kiln and the consequent production of uncondensed vapors. This may occur for example by backward travel of air through the condenser and vapor outlet pipe.

I have found a good indicator for the purpose of showing the kiln attendant that the necessary slight superatmospheric pressure is maintained in the kiln to prevent access of air, may consist of a thin, elongated tube leading out and down from about the bottom of the kiln to the open air. Dripping from this tube indicates that the necessary slight superatmospheric pressure is present in the kiln, thereby'excluding the entry of air thereto. If uncondensed steam issues from the end of the tube, however, this shows that the steam supply is unnecessarily great and may be shut oif somewhat.- A similar result can, of course, be secured by the use of a thermostatic control for the steam supply, and where the steam pressure is irregular or high a constant pressure reducing valve may advantageously beused. The rate of production of turpentine and pine oils is greatest at or a short time after the first complete condensation is obtained and gradually decreases thereafter. I have found that it is complete enough for practical purposes in about eight to ten hours after. the condensation begins, thus making the entire treatment cover about ten to twelve hours. At the end of about this time the Wood is thoroughly heated through and a considerable portion of its moisture extracted. This long thorough treatment serves to prevent case hardening and the consequent cracking or checkingpf the lumber upon further drying.

In order to secure circulation of the steam throughout the lumber during the steam treatment, the steam is preferably admitted to the kiln in'such manner as to create a continuous circulation, as for example the steam from twenty to ninety pounds per square After the steam treatment-is finished, the

by-product kiln is preferably opened up, the kiln trucks removed and the lumber piled thereonmay be permitted to cool in the open an. In this manner" moisture is the drying and conditioning process is completed.

The following example is given to show how the inventlon was carried out in, one case in connection with yellow pine lumber, partly long leaf pine and partly short leaf pine, but such example is not intended to impose limitations upon the invention:

A Icy-product kiln was constructed about 12% ft. high, about 11 ft. wide and about 21 ft. long. In order to insure that the doors should close tight, a rubber hose used for supplying part of the condensing water was run around thedoor flanges and the doors closed on it, after which the water was turned on through this hose, thereby affording an efl'ective air seal.

A truck-load of yellow pine lumber piled for ordinary kiln drying was placed in this kiln for the steam treatment. Same contained about 3,906 board feet. The lumber was principally heart boards, and containing a out of long leaf pine. The kiln had a Vapor pipe connected thereto at its top and leading through an eficient cold water condenser to an automatic separator with an air vent at the exit side of the condense-r.

Steam was turned on through five pipes, one an open end pipe running in through the end of the kiln, and four spray pipes with steam jet openings in their sides. One of these spray pipes was located at the bottom of the kiln and another at the top, and of the remaining two, one was on one side of the kiln low down and the other on the opposite side higher up, so as to create circulatory rotation of the steam through the layers of piled lumber.

Steam from a pressure line carrying about ninety pounds per square inch of steam pressure was admitted to the kiln for a period of about two hours, during which time vapors finally becoming extremely dense and smelling stronglyof turpentine passed through the vapor pipe and condenser without any distillate being obtained,although the condenser was kept cold by running water. At

llll

the end of this time condensation became substantially complete, the vapors were no longer visible, and the steam was shut off from all the pipes, except the last two circulatory spray pipes referred to above, through which sufficient steam was continued to be admitted to maintain a slight supera-tmospheric pressure in the kiln. The portion of the distillate rising to the surface of the condensed water was removed and measured from time to time. It will be noted that while in general these measurements were made every hour, no measurements were made during the lunch hour or during the night. Steam was first turned on at 8 :30 a. m. The temperature of the interior of the kiln was taken from time to time at a point giving a good average of temperature and same, after coming up gradually to about 97 C. at the time when the densest fumes were evolved, increased to about 98 to 99 C. where it remained substantially constant during the run. The results obtained are given in the following table:

Time. Hours. Percent. g b

10:30 a. m 2 4,405 4,405 23.5 .3 11:30 a. m 2 3,420 7,825 41.7 .53 12:30 .m we 5 2,715 10,600 55.5 .72 2:30 a 1,270 11,870 63.0 .80 3:30 7 1, 090 12, 900 69. 0 as 4:30 8 880 13, 840 74. o .94 5:30 9 1,075 14,915 80.0 1.02 7:00 22 '3, s30 18, 100. o 1. e7

' Including Skimmiugs.

The total yield obtained was at the rate of 1.27 gallons per 1,000 board feet-of lumber. or 4:.8- c. e. per board foot. On steam distillation of this material ityields about 8&9?) of crude wood turpentine and about 16% pine oils.

I havefound that the objectionable smell usually ascribed to wood turpentine can be largely elin'linated by the presence of a very slight amount of sodium hydroxide during steam distillation; A very small amount is suflieient, say less than one-hundredth of one per cent of the quantity of turpentine distilled.

After the run was completed the kiln was opened and the lumber truck removed and the lumber permitted to cool in the open air; After cooling, it was run into a dry kiln having steam pipes in the bottom, and regulated vapor outlets to a stack, and when' dried, which took substantially less time than with green wood, was good quality lumber free from drying checks or splits.

The accompanying drawing forming a part of this specification shows one fornrof apparatus in which the process of my invention can be carried out. Fig. 1 of said kiln doors.

In said drawings the kiln is designated by reference numeral 10. It is shown closed at one end and having doors 11 at the opposite end. Means are provided for hermetically sealing the doors, as, for example, a rubber hose 12 may be placed. in grooves provided in the doors and door frames, and after closing the doors thereon 'water may be turned into the hose to expand the same, the water being conveniently used in the condenser jacket.

The lumber trucks 13 having lumber l-l pile'd in open order there-on are run in on tracks 15. The entire series of trucks with lumber thereon is preferably introduced into treatment is completed.

Steam heating coils 16 are provided and are preferably placed under the tracks 15. The steam is admitted through spray pipes. In the form shown it is passed in through a central spray pipe 17, which is provided with lateral connections 18 leading to the side pipes 19, which communicates with the vertical spray pipes 20. i

The steam and vapor outlet pipe 21 is preferably provided at the top of the kiln at or near the middle thereof, and the vapors and steam carried thereby are condensed in a condenser 22, theturpentine. pine oils. et c., rising through the top of the receptacle 23 and being discharged to storage at 2% while the condensed steam runs all from the bottom of the container 23 through the outlet pi-pe 25.

A sealed outlet pipe forcondensed steam is preferably provldedat the bottom of the kiln, such pipe being indicated by the re ference numeral 26. Reference numeral 21' is applied to designate a pipe to show superatmospheric pressure. This is a small pipe providing substantially a. vent for the hermetically closed kiln and serves to indicate the presence of superatmospheric pressure in the kiln by the discharge of a small jet of steam therethrough during operation.

It will be observed that by my improved process numerous advantages are obtained. The delivery of heat units to the wood during the b 'product kiln treatment isv much more rapid than is possible in the case of ordinary kiln drying, wherein the delivery to the lumber of so much heat during a period of aboutten to twelve hours would produce case hardening with its attendant evils. The long slow steaming of the wood at substantially the boiling pointof water drives off much moisture with entire absence of case hardening and at the same time secures substantial yields of the valuable resinous materials. The lumber is piled on trucks and handled in the manner usual with kiln drying and such slight extra labor and power as is required to run the trucks with the sawn lumber piled thereon into and out of the by-product kiln is more than compensated by the short time of treatment required in the dry kilns. Where dry kilns are already installed no expensive plant requirements are involved, since one out of say every seven kilns can be equippedwith the necessary piping, air tight doors, vapor pipe and condenser to make it available for use as a by-product kiln, and the remaining six kilns can take care of the final step of drying the lumber steam treated in such by-product kiln, and there is no reduction and may be a substantial increase in output of well dried and seasoned lumber.

I claim:

1. The process of producing dried sawn lumber of good quality and obtaining byproducts therefrom, which consists in placing resinous sawn lumber in open order on trucks, introducing same into a kiln closed, except for a vapor outlet, in-troducin live steam into the kiln until the air is displaced, then continuing the supply of live steam at a reduced rate sullicient, however, to main-' tain a slight supcratmospheric pressure in the kiln, while condensing the issuing steam and vapors, and completing the drying of the lumber whilestill on said trucks.

In the process of producing dried yellow pine sawn lumber of good quality and obtaining turpentine and pine oil by-products therefrom, the ste s which consist in introducing resinous yel ow pine lumber into a tightly closed kiln, running steam into said kiln until the kiln and lumber are heated to substantially the boiling point of water while permittingany vapors to escape freely from the kiln, and then continuing the steam supply at a reduced rate sufficient, however, to maintain slightly superatmospheric pressure within the kiln while collecting and condensing the vapors whereby substantial yields of turpentine and pine oil are obtained, and completing the drying of the lumber while still on said trucks.

3. The process of producing dried sawn yellow pine lumber of good quality and obtaining turpentine and pine oil by-products therefrom, which consist in piling resinous yellow pine sawn lumber on kiln trucks, introducing same into a tightly closed kiln, turning steam into said klln in substantially large quantities for a period of about two to prevent access of air thereinto while condensing and collecting the vapors produced,

whereby substantial y1elds of turpentine and pine oils are obtained, then removing the lumber on its trucks from the kiln and permitting to cool in the open air, and completing the drying of the lumber while still on said trucks.

4. The rocess of producing dried sawn lumber of good quality and obtaining byproducts therefrom, which comprises introducing resinous sawn lumber in open order into a tightly closed kiln supplied with steam heating coils and steam induction means, supplying steam through the steam induction means and applying heat by means of the steam-heating coils, condensing the issuing vapors with the resinous material going over with the steam, continuously supplying fresh steam by the steam induction means to replace the condensed steam and to maintain superatmospheric pressure within the kiln, and further drying the lumber after removal of by-products.

In testimony that I claim the foregoing,

I have signed my name hereto.

' WVILLIAM H. MASON. 

